1. Field of the Invention
The present invention relates to an inkjet liquid discharge head for discharging liquid such as ink from discharge ports and a substrate therefor, the liquid being discharged by the steps of applying thermal energy thereto using heating elements provided in flow paths through which the liquid flows so as to cause film boiling in the liquid, and then discharging the liquid using bubbles formed by the film boiling.
2. Description of the Related Art
Hitherto, as a liquid discharge head, in particular, as an inkjet liquid discharge head, for example, the structure has been disclosed in U.S. Pat. No. 4,567,493 in which thermal energy is applied to liquid filled in ink flow paths by heaters provided therein to form bubbles for discharging ink from discharge ports communicating with the ink flow paths.
In the liquid discharge head disclosed in U.S. Pat. No. 4,567,493, a heat accumulating layer, which is a lower layer made of SiO2 for preventing heat generated by a heater from being dissipated, is formed on a silicon (Si) substrate, and a heater film which is a heat generating resistive layer made of HfB2 is further provided on the heat accumulating layer described above. Wires made of aluminum (Al) for supplying electricity to the heater film described above are disposed with a predetermined space interposed therebetween to form a predetermined pattern. A region between the wires disposed with a predetermined space interposed therebetween is a heat generation region which generates heat when current is supplied to the heater film. On the heater film and the wires, there are provided an insulating layer made of SiO2, which is a first upper protective layer, for isolating ink from the heater film and the wires; a protective layer made of tantalum (Ta), which is a third protective layer, for protecting the heater film from impact which is generated when a bubble formed in the ink by film boiling is defoamed; and a resinous protective layer, which is a second protective layer provided in a region other than the heat generation region, for preventing the ink from permeating through the insulating film.